The present invention generally relates to fluid spray guns and more particularly to supply valves for compact fluid spray guns used for paint spraying, fiberglass spraying and plasticizer spraying, etc.
The above types of spray guns normally contain a handle and a trigger lever(s) located adjacent the handle so that the operator can easily operate the gun. One trigger lever is used for operating a supply valve used to control flow of fluids e.g. paint supply(s), catalyst, resin, etc. and air for mixing, shaping, etc. It is possible to utilize one trigger element which in its initial arc of movement operates the supply valve and in its latter arc of movement operates the various metering systems that control the aforementioned flows of materials.
The prior art supply valve in spray guns have generally used spool or needle valves. These valves were biased in the closed direction by springs and the fluid flow of the open valve worked against the spring. This required large springs and large actuation forces to open the valves. Also with these valves, the fluid was introduced radially and exited axially. This requires additional space in the gun for the transmission of fluid from the inlets to the outlet of the valve.
Past attempts to provide supply valves have had unsatisfactory results due to among other things, their length, the number of parts, sealing systems, material flow resistance causing hand fatigue of the operator in operating the supply valve and keeping the triggering lever in position, etc.
It is an object of this invention to overcome the above unsatisfactory results by providing a compact spray gun and supply valve system which has only a few parts.
An object is to provide a supply valve which is compact in length.
It is a further object to utilize the pressure of the material flowing through the spray gun to assist a spring to bias the shut-off valve to its closed position while also providing no resistance to the actuating trigger when the shut-off valve is in its open flow permitting position.
The apparatus includes a first valving element comprising a reciprocating valving sleeve with a passageway therethrough. Ends of the sleeve have similar cross-sectional areas and are subject to the pressure of the material(s) flowing through the valve when the valve is opened. This equal area causes the sleeve to be fluidically balanced when the supply valve is open. A spring biases the reciprocating valving sleeve to its closed position and the pressure upstream of the sleeve applies a force to an upstream end of the reciprocating valving sleeve to assist the spring. The spring surrounds the reciprocating valving sleeve and is located in a chamber sealed from egress of the material flowing through the reciprocating valving sleeve.
Downstream of the reciprocating valving sleeve is a valving chamber containing a spherical, free floating second valving element which cooperates with the downstream side of the hollow passageway of the reciprocating valving sleeve. When the gun trigger is released, the spring bias forces the reciprocating valving sleeve to abut the spherical valving element to seal off flow of spray gun material through the passageway. The pressure of this material helps hold the reciprocating valving sleeve against the spherical valving element.
When the operator applies a force to the trigger lever, it moves the reciprocating valving sleeve and opens the valve in opposition to the force of the spring. As the reciprocating valving sleeve moves away from the spherical valving element, material beings to flow through the passageway in the reciprocating valving sleeve and through a valving chamber so that the reciprocating valving sleeve has its downstream end acted on by the pressure of the material flowing through the spray gun. The downstream pressure acts in opposition to the upstream pressure of the material to allow the reciprocating valving sleeve to be in a pressure balanced condition as concerns the pressure of the material flow. This admits of a smoother actuation of the supply valve and reduces the hand pressure of the operator in holding the valve open. Thus hand fatigue of the operator is reduced.
The downstream valving chamber housing the free floating spherical valving element can be cylindrical and has one end open to the reciprocating valving sleeve and an opposite end having at least two outlets therein.
The outlets are spaced at the same radial distance from the flow axis of the supply valve. The radial distance is at least equal to, or greater than the radius of the free floating spherical valving element. This causes the material flow to divide as it exits the outlets of the passage in the reciprocating valving sleeve and flows over the spherical valving element to help keep it centered on the axis of the reciprocating valving sleeve. The spherical element is free floating so it can rotate to provide changing valve surfaces for the supply valve thus improving its useful life. The spherical element also is able to bounce around in the cylindrical valve chamber to assist in cleaning the supply valve.
The valving end of the reciprocating valving sleeve preferably has a rounded configuration to match the configuration of the spherical valving element. Alternatively the valving end could be chamfered. Even a flat perpendicular edge could be used.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.